The invention relates to a process for preparing substituted 1,2-naphthoquinone-(2)-diazide-4-sulfonic acid esters starting from correspondingly substituted .beta.-naphthol. The invention relates also to their use in a radiation-sensitive mixture with which corresponding recording materials can be prepared.
Naphthoquinonediazidesulfonic acids are used as photosensitive compounds for radiation-sensitive mixtures, such as for preparing photoresist mixtures or for preparing print forms (J. Kosar, "Light-Sensitive Systems", John Wiley & Sons, New York, chapter 7.4, 1965).
Their preparation starts from benzene- or naphthalenesulfonic acids which are substituted by hydroxyl groups and which are nitrosated with sodium nitrite in dilute aqueous acid, and the nitroso compound formed is isolated from the unreacted starting substances. The nitroso compound is then reduced to the corresponding amino compound which is separated off and resuspended in water in order to form the diazide compound at lower pH in the presence of sodium nitrite.
A disadvantage of this process is its multistage nature and the necessity of keeping the byproducts formed in aqueous solution and separating them from the main product formed in each case as a precipitate and purifying the product. Associated with this are, in addition to high production costs, low yield and insufficient product purity.
European Patent Application, Application number 88104043.0 discloses a process for preparing halogen-, nitro- or alkyl-substituted aryldiazidesulfonic acids in which the starting point is an arylsulfonic acid substituted by at least one hydroxyl group, and in which nitrosation and reduction of the resulting nitroso compound is carried out in the alkaline pH range. The amino compound is then converted into a sulfamate, the sulfamate derivative is mixed with a diazotizing agent and, after acidification, the aryldiazidesulfonic acid is obtained. In this process, the reaction product formed after each reaction step and suitable for further reaction remains in solution, but the final product is not free of isomeric compounds.
Nucleus-substituted 1,2-naphthoquinone-(2)-diazide-4-sulfonic acid esters are of interest for preparing photoresists. Their photosensitivity range is extended by the substituents.
To produce such photoresists, it is important that an economical process for preparing the photosensitive components is available.